Re: [linux-lvm] Software raid on top of lvm logical volume

["Michael T. Babcock" <mike@mikebabcock.ca>]

Theo Van Dinter wrote:

>On Thu, Oct 28, 2004 at 12:02:06AM +0200, Eric Monjoin wrote:
>  
>
>>I would like to know if it's possible (works perfectly) to create a 
>>software mirror (md0) on top of  2 LVM logical volumes :
>>    
>>
>
>You'd usually want to make your raid devices first, then put LVM on
>top of it.  I can't really think of any benefits of doing it the other
>way around.
>  
>

I've thought about this numerous times -- there is the distinct resizing 
advantage.  Namely, if I create a software RAID partition, I can't 
resize it afterward without destroying it.  I have for example, on 
occasion, had three disks set up where 1/3 of each was devoted to a 
RAID-0 very fast striping set for data transfers that had to be fast but 
if they were lost it wasn't critical, and 2/3 was set up as RAID-5 for 
reliability of another set of data.

I understand this may not be optimal in some situations, but some of us 
don't have thousands of dollars for SCSI HW RAID controllers.
-- 
Michael T. Babcock